Pupilometer for pupil center drift and pupil size measurements at differing viewing distances

ABSTRACT

The present invention generally provides improved devices, systems, and methods for measuring characteristics of at least one eye, and particularly for measuring the physiological changes in eyes under different viewing conditions. An exemplary embodiment provides a pupilometer which measures any changes in location of a pupil center with changes in viewing distances. As the eye often moves significantly during viewing, the pupil center location will often be measured relative to a convenient reference of the eye such as an outer iris boundary. Pupil size may also be recorded, and the measurements from both eyes of a patient may be taken simultaneously. Exemplary embodiments may be configured so as to allow the vergence angle between the eyes to vary with differing viewing distances, regardless of whether one or both eyes are being measured.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application which claims the benefit of priorityfrom U.S. patent application Ser. No. 11/088,010 filed on Mar. 22, 2005,the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention generally relates to optical diagnosis and measurementsof the eye, and in particular embodiments provides devices, systems, andmethods for measuring the changes in pupil position, location, and thelike with changes in distance and/or other viewing conditions.

Presbyopia is a condition that affects the accommodation properties ofthe eye. As objects move closer to a young, properly functioning eye,ciliary muscle contraction and zonular relaxation allow the lens of theeye to become rounder or more convex. This increases the optical powerof the lens and enhances the ability of the eye to focus at neardistances. Accommodation can allow the eye to focus and refocus betweennear and far objects.

Presbyopia normally develops as a person ages, and is associated with anatural progressive loss of accommodation (sometimes referred to as “oldsight”). The presbyopic eye often loses the ability to rapidly andeasily refocus on objects at varying distances. There may also be a lossin the ability to focus on objects at near distances. Although thecondition progresses over the lifetime of an individual, the effects ofpresbyopia usually become noticeable about the age of 45 years. By theage of 65 years, the crystalline lens has often lost almost all elasticproperties and has only limited ability to change shape. Residualaccommodation refers to the amount of accommodation that remains in theeye. A lower degree of residual accommodation contributes to more severepresbyopia, whereas a higher amount of residual accommodation correlateswith less severe presbyopia.

Work is now underway on developing methods and devices for treatingpresbyopia. These treatments often seek to provide vision approachingthat of an emmetropic eye. In an emmetropic eye, both distant objectsand near objects can be seen using the accommodation of the eye. Toaddress the vision problems associated with presbyopia, traditionaltreatments have included reading glasses and the like. Reading glassesadd plus power diopter to the eye of an individual, thus allowing theeye to focus on near objects and maintain a clear image. Presbyopia hasalso been treated with bifocal eyeglasses, where one portion of the lensis corrected for distance vision and another portion of the lens iscorrected for near vision. Although such approaches can provide clearvision when the eye is looking through the appropriate lens, otherobjects in the field of view may be distorted. Still further alternativetreatments have been employed, including monovision (in which one eye iscorrected for distance vision while the other eye is corrected for nearvision) and the like. Many of these therapies have been successful forat least some patients, but none has been shown to provide ideal viewingcapabilities for all patients throughout a wide viewing distance range.

In the field of refractive surgery, certain ablation profiles have beensuggested for treatment of presbyopia. The goal of these presbyopiaablation profiles is often to increase the range of focus of the eye,rather than attempting to restore a combination. Many of these ablationprofiles can provide a wider depth of focus, although in many cases withsome compromise. U.S. patent Ser. No. 10/738,358, filed on Dec. 5, 2003and entitled “Presbyopia Correction Using Patient Data”, the fulldisclosure of which is incorporated herein by reference, describespromising approaches for treatment of presbyopia using laser ablationand other refractive correction techniques. Many of these proposedrefractions are adjusted or tailored for a specific patient.

While the newly-proposed presbyopia treatment approaches show greatpromise, still further enhancements in the field would be helpful. Inparticular, presbyopia treatments may benefit from increased knowledgeregarding the response of the eye to different viewing conditions. Thismay, for example, facilitate developing appropriate classes of treatmentshapes through a better understanding of typical physiological changesto the eye when the patient changes between viewing at near and fardistances. Improved devices for measuring the eye's response to changesin viewing distances may also help tailor or select appropriatetreatments for a particular patient, or may be used to exclude certainpatients from treatments which would be inappropriate and/or result invisual acuities that are less than may otherwise be available throughalternative treatments.

In light of the above, it would be advantageous to provide improveddevices, systems, and methods for measuring and/or diagnosing eyes. Itwould be particularly advantageous if these improved techniquesfacilitated developing and/or tailoring of refractive correctionprescriptions for classes of patients or individual patients.

BRIEF SUMMARY OF THE INVENTION

The present invention generally provides improved devices, systems, andmethods for measuring characteristics of at least one eye, andparticularly for measuring the physiological changes in eyes underdifferent viewing conditions. An exemplary embodiment provides apupilometer which measures changes in location of a pupil center withchanges in viewing distance. As the eye tends to move significantly(voluntarily and/or involuntarily), the pupil center location will oftenbe measured relative to a convenient reference of the eye such as anouter iris boundary. Pupil size may also be recorded, and themeasurements from both eyes of a patient may be measured substantiallysimultaneously. Exemplary embodiments may be configured so as to allowthe vergence angle between the eyes to vary with differing viewingdistances, regardless of whether one or both eyes are being measured.

In a first aspect, the invention provides a pupilometer comprising anoptical sensor. A sensing optical path couples the sensor with an eyemeasurement location. A variable distance viewing target system iscoupled to a processor, which is also coupled to the sensor. Theprocessor is thereby capable of determining a relationship betweenchanges in viewing distance between the eye location and the viewingtarget and pupil center drift of a pupil of an eye disposed at the eyelocation.

In many embodiments, the processor will be configured to determine therelationship between changes in viewing distance and pupil center drift.The viewing target will often have an associated near viewingconfiguration and an associated far viewing configuration, the target inthe far viewing configuration being optically separated from the eye bya greater viewing distance than in the near viewing configuration. Theviewing target with the near viewing configuration will typically beoptically separated from the eye by no more than about one meter. Theviewing target with the far viewing configuration will typically beoptically separated from the eye by at least three meters, often by fivemeters or more. One or more intermediate viewing distance configurationsmay also be provided, with the viewing distances optionally beingvariable throughout a range.

In many embodiments, the viewing target will be coupled to the eyemeasurement location by at least a portion of the sensing optical path.This can facilitate measurements from along the optical axis of the eye.In some embodiments, a target optical path will couple the target to theeye measurement position, with at least a portion of the target opticalpath being offset from the sensing optical path. An optical path lengthof the target optical path will typically vary with changes inconfiguration of the viewing target system. In some embodiments, thetarget optical path and the sensing optical path may be separated alongsubstantially their entire length, particularly when using off-axispupil measurements.

The changes in configuration of the viewing target may be effected byany of a variety of path length altering approaches including movabletarget images, a plurality of alternatively selectable target imageshaving differing target optical path lengths, an optical zoom, a turretof alternative selectable optical elements such as different mirrorassemblies, lenses or lens sets, or the like. By using zoom lenses andthe like, the physical distance between the target and eye need notchange.

Optionally, the pupilometer may comprise a binocular structure having anat least partially separate sensing optical path coupled to another eyemeasurement location for measurements of the patient's other eye. Theprocessor can be configured to determine the relationships betweenviewing distance and pupil drift of each eye separately, with themeasurements often being taken at the same time. In some embodiments, aseparate sensor may be provided for measuring pupil size, centerlocation, and/or the like of the other eye. In other embodiments, thesame sensor may be coupled to the other eye measurement position by theother sensor optical path, so that one sensor measures characteristicsof both pupils. The sensor will often comprise at least one imagecapture device such as a charge couple device (“CCD”) sensitive toinfrared (“IR”) light, or the like. When a single image capture deviceis used, a sensor surface of the image capture device may be separatedinto portions associated with each eye, or images generated thereon mayalternate between the left and right eyes of the patient.

In binocular pupilometer embodiments, optical axes may extend fromadjacent each eye measurement location toward the viewing target. Avergence angle between the first and second optical axes may change whenthe viewing target changes between a near viewing configuration and afar viewing configuration. Accommodating such changes in vergence anglemay help provide a more natural physiological response to changes inviewing distance, and may thereby enhance pupil size and/or pupil driftmeasurements with changes in viewing distances.

In many embodiments, the optical path will image at least a sufficientportion of the pupil and an outer iris boundary of the eye onto an imagedetection surface of the image capture device. This may allow thepupilometer to determine a center of the pupil relative to a center ofthe outer iris boundary. Optionally, a variable brightness illuminationsource may be optically coupled to the eye measurement location. Theprocessor can be coupled to the variable illumination source so as todetermine a relationship between illumination of the eye and pupil driftor pupil size. The processor may record a plurality of relative pupilcenters and associated pupil sizes and viewing distances.

In another aspect, the invention provides a binocular pupilometercomprising an image capture system and a first sensing optical pathcoupling the image capture system with a first eye measurement location.The first sensing optical path may have a first optical axis extendingfrom the first eye location. A second sensing optical path may couplethe image capture system with a second eye measurement location. Thesecond sensing optical path may have a second optical axis extendingfrom the second eye location. A variable distance viewing target systemwill have a target image as well as a first configuration and a secondconfiguration. The target system will have a first viewing distancebetween the first and second eye locations and the target image when inthe first configuration. Similarly, the target system will have a secondoptical viewing distance between the second image and the first andsecond eye locations when in the second configuration. The secondviewing distance is greater than the first viewing distance, and avergence angle between the first optical axis and the second opticalaxis varies when the target system changes between the firstconfiguration and the second configuration. A processor is coupled tothe image capture system and the viewing target system. The processor isconfigured to determine a relationship between a change in viewingdistance between the eye and the viewing target, and a pupil drift of apupil of an eye disposed at each eye location.

In another aspect, the invention provides a pupil measurement methodcomprising capturing a first image of a first eye while the first eye isviewing at a first viewing distance. A second image of the first eye iscaptured while the first eye is viewing at a second viewing distance.The second viewing distance is different than the first viewingdistance. Pupil center drift of the first eye is determined from thefirst and second captured images of the first eye.

In many embodiments, first and second images of a second eye will becaptured while the second eye is viewing at the first and second viewingdistances, respectively. The eyes may be viewing at similar distancessimultaneously. Pupil center drift of the second eye may be determinedfrom the first and second captured images of the second eye. A vergenceangle between optical axes of the first and second eye may change withthe changes in viewing distance.

Pupil center drift may be determined by determining a first center of afirst pupil of the first eye relative to a center of an outer irisboundary of the first eye from the first image. A second center of thepupil of the first eye relative to the center of the outer iris boundaryof the first eye may similarly be determined from the second image. Theeye will often move between the acquiring of the first and secondimages.

Pupil size at the first and second viewing distances will often bemeasured, and intermediate distances (optionally comprising one or moreintermediate distance, and in some embodiments including a continuousrange of intermediate distances) may be used for measurements.Variations in illumination brightness may be provided so as to determinea relationship between brightness and pupil size at differing viewingdistances.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a pupilometer system for measuringpupil characteristics such as pupil center drift, pupil size, and/or thelike with changes in viewing distance.

FIG. 2 illustrates an image captured by an image capture device of thesystem of FIG. 1, and also shows changes in pupil center location orpupil drift.

FIGS. 3A and 3B graphically illustrate a relationship between pupilcenter drift and viewing distance for the left eye and right eye of apatient, respectively.

FIGS. 4A and 4B schematically illustrate methods for determining pupilcenter drift from different images taken at different viewing distancesby identifying centers of a pupil and an outer iris boundary.

FIG. 5 schematically illustrates changes in vergence angle with changesin viewing distances.

FIG. 6 schematically illustrates some of the optical elements and othercomponents of a pupilometer.

FIG. 7 illustrates an alternative embodiment of a binocular pupilometer.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally provides improved devices, systems, andmethods for measuring characteristics of the eye, particularly undervarying viewing conditions. In exemplary embodiments, the inventionprovides pupilometers capable of measuring both pupil size and pupilcenter drift as a function of varying viewing distances. The device willoften use one or two cameras, and will generally have an optical trainfor each camera which provides a field of view that is sufficient tocapture a sufficient portion of the outer boundary of the iris so as todetermine the iris center. Image processing software will typicallyidentify both the iris and pupil boundaries and centers, and the sizeand relative center positions will be computed. Since the iris centerlocation is substantially independent of the pupil size, the pupilcenter can be tracked in reference to the iris center.

Along with measurements in pupil drift and pupil size, the presentinvention may also provide additional characteristic measurements withchanges in viewing distance, illumination or brightness, or the like.For example, measurements of the roundness of the pupil may be obtained,hysteresis or differences between the physiological characteristics ofthe eye when viewing conditions are changing in one direction (forexample, from a far viewing distance to an intermediate viewingdistance) versus another direction (in our example, changing from a nearviewing distance to the intermediate viewing distance), In someembodiments, response time or delays between changes in viewingconditions and, physiological responses, differences between the twoeyes of a patient, and/or the like may be determined. Hence, althoughthe initial application for the present invention may be for developmentor tailoring of presbyopia prescriptions, the invention may also findapplications in other fields, such as measuring anisocoria, detectingdrug abuse and/or opiate addiction, and the like.

Referring now to FIG. 1, pupilometer 10 generally measures pupilcharacteristics of an eye E. Eye E will generally be disposed at an eyelocation 12, and will be coupled to an optical sensor such as camera 14by an optical path 16. A variable distance viewing target system 18presents a viewing target eye E, the target being at a variable opticalviewing distance from eye location 12. The viewing target system 18 andcamera 14 are coupled to a processor 20.

Referring now to FIGS. 1 and 2, viewing target system 18 will typicallyhave a near viewing configuration and a far viewing configuration, withthe target being displayed to eye E at viewing distances which changewith the change in configuration of the target system. The eye Eundergoes a variety of physiological changes with change in viewingdistances. In a young emmetropic eye, ciliary muscles change a shape ofthe lens of the eye to change its optical power as the viewing distancechanges. Additionally, the size of a pupil P of eye E varies withchanges in the viewing distance. More specifically, pupil P contractswhen the patient's focus changes between viewing a target at arelatively far distance to one at a nearer distance. Pupil P alsocontracts and/or expands with changes in brightness or illumination,with these changes in illumination optionally including changes in thebrightness of the object or target being viewed, changes in the ambientlight around the viewing target, and the like.

Along with changes in the overall size of pupil P when the eye E issubjected to different viewing conditions, the location of the pupilcenter C may also change. It should be noted that this change inlocation of the pupil center may be separate from and in addition to anyoverall movement of the eye. In other words, even if the eye E were toremain at an overall fixed location in space so that the cornea and theretina of the eye did not move, as the pupil P contracts from a firstpupil configuration to a smaller pupil configuration P′, the center C ofthe pupil may undergo a corresponding change in location to a new pupilcenter C′. This change in pupil center location is encompassed withinthe term “pupil center drift” as that term is used herein.

In the above description of pupil center drift, it was assumed that theoverall eye E was not moving. The eye, however, does move. Also, when aperson goes from looking at an object at a far distance to an object ata very close distance, the eyes gradually turn inward so that each eyeis pointed toward the same location in space. By accommodating andproviding for this change in vergence angle, pupilometer 10 may provideenhanced physiological measurement accuracy for changes in viewingdistance. Along with voluntary movements of the eye as the patient looksat targets in different locations, the eye also undergoes involuntarymovements. In other words, even when the patient is holding steadyfixation on a visual target, eye movement still occurs. This involuntarymotion will often include two-dimensional lateral movement of the pupilP as the eye rotates in its socket, cyclo-torsional rotation of the eyeabout its optical axis, and the like. These movements can be quite rapidand of significant size when attempting to measure the changes in pupilcenter location relative to the adjacent structures of the eye.

So as to allow accurate analysis of the optical properties of the eyewhen the pupil changes configuration from viewing at a far distance P toa near viewing configuration P′, it will often be advantageous tomeasure the change in pupil center C from its initial position to arevised center location C′ relative to some other tissue of eye E.Toward that end, center location C will often be measured relative tosome visible reference structure on the eye, and ideally relative to theouter iris boundary B. The outer iris boundary is generally adjacent toa limbus LI of the eye. The limbus is the interface between the clearcornea and the white sclera of the eye. The limbus, however, is more ofa transition zone between the cornea and the sclera, rather than a sharpboundary. Additionally, the scleral tissues at the interface with thecornea may be clear, so that the limbus may, at least in part, comprisethe interface between two clear tissues. For these reasons, there may beadvantages in making use of the outer boundary B of iris I as areference location for monitoring pupil center drift.

Referring still to FIGS. 1 and 2, FIG. 2 generally shows an image of eyeE as obtained by camera 14 during use of system 10 (along with asuperimposed contracted pupil P′, pupil center locations C, C′, and thelike). Camera 14 will generally comprise an image capture device orother optical sensor capable of detecting optical information sufficientfor measurement of the pupil center location, pupil size, outer irisboundary B size and/or location, the location of other additional oralternative reference structures on the eye, and the like. In theexemplary embodiment, camera 14 comprises a charge couple device (“CCD”)which is sensitive to infrared light.

Eye location 12 will generally be defined at least in part by astructure to be engaged by tissues around eye E, such as an eye cup orthe like. In binocular versions of pupilometer 10, mechanisms whichallow variations in distances between the eyes will often be provided,and the optical path 16 from the eye location 12 to camera 14 may beisolated from a surrounding room environment (and optionally isolatedfrom at least a portion of the other optical path of a binocularpupilometer) using a shield, housing, drape, or the like.

Optical path 16 will often include additional optical imaging elementswhich are omitted from the simplified schematic of FIG. 1, includingimaging lenses and the like, so as to image an iris I of eye E onto animage sensing surface of camera 14. Additional imaging components, suchas apertures, filters, beam splitters, and the like may be used at leastin part to define optical path 16, and the optical components willtypically be held in place by an appropriate metallic or polymer supportstructure, which may be integrated into a housing extending from an eyecup adjacent eye location 12 to and/or beyond camera 14.

Camera 14 will typically comprise a CCD sensitive to infrared light,although a wide variety of alternative image capture structures may alsobe employed, including complementary metal-oxide semiconductor (“CMOS”)image capture devices, HRDC image capture devices, and the like. Camera14 may comprise, for example, a GW-902H model camera commercialized byGENWAC, INC. of New York and manufactured by WATEC CO., LTD. of Japan,which may take images using IR illumination with a wavelength of 880 nm.A variety of alternative cameras, imaging structures, or other sensorsmight also be used, including a GW-902B model camera from GENWAC; a TeliCE camera which may take images using IR illumination with a wavelengthof 940 nm, and/or another camera selected from those commercialized asthe CS8300B series by TOKYO ELECTRONIC INDUSTRY CO., LTD of Japan; a4900 model series camera commercialized by COHU, INC., ElectronicsDivision of San Diego; and the like. Optical path 16 will typicallyimage a field of view of at least about 10.5 mm by 14.0 mm (measured atthe plane of the iris of the eye), onto the image sensing surface, so asto image a sufficient portion of the iris with camera 14.

Processor 20 of pupilometer 10 will often comprise a personal computer,as illustrated in FIG. 1. Processor 20 will typically include a display22 for showing an image of the structures of the eye, graphicalrepresentations of the pupil drift and any other physiologicalcharacteristic measurements, and the like. Processor 20 will typicallyinclude a tangible media 24 embodying a machine readable code withprogramming instructions and/or data for implementing the method stepsdescribed herein. Tangible media 24 may comprise a magnetic recordingmedia such as a floppy disk or magnetic tape, an optical recording mediasuch as a CD or a DVD, an electronic media or memory such as a RAM orROM, a non-volatile memory such as a USB memory stick device, or thelike. In some embodiments, the machine readable code and/or data may betransmitted via an Internet, an intranet, a wireless transmissiondevice, an optical network or cable, an electrical coaxial or twistedpair cable, or the like. When in the form of a personal computer,processor 20 will typically include user input devices such as akeyboard and/or mouse, input and output ports, software such as anoperating system and a pupilometer user interface. Alternative processorstructures might also be used, including specialized processor boards,distributed data software and/or hardware arrangements, and the like.

When pupilometer 10 is in use, eye E will often be illuminated with anillumination source have a wavelength suitable for imaging of the eye bycamera 14. For example, eye E may be illuminated by one or morelight-emitting diodes (LEDs). Illumination may also be provided byvariable distance target system 18, optionally by changing a brightnessof a viewing target at a desired optical distance from the eye. In manyembodiments, both the viewing distance and brightness of the viewingtarget or other variable illumination will be controlled by processor 20using command signals sent to variable distance target 18 and/or anyadditional illumination source. Imaging signals will generally begenerated by camera 14 and transmitted to processor 20.

Under infrared illumination, the pupil P of eye E will appear relativelydark to camera 14, as the infrared energy is not directly reflected bythe clear corneal structure. The iris I surrounding the pupil P willpresent a much light shade to camera 14, with the white scleral tissuesurrounding the iris presenting a still lighter shade. The relativelyhigh contrast borders between the pupil and iris, and between the outeriris boundary and the surrounding tissues have a sufficiently highcontrast image for determining pupil and iris size and center location.

Referring now to FIGS. 1-4B, a location of the iris I (and all othertissues of the eye E) will change with saccadic and other movements ofthe eye. While eye E is viewing at a first, relatively near viewingdistance (as determined by variable viewing target 18 under the commandof processor 20), image capture device 14 obtains an image of the eye.Using the difference in relative contrast between the pupil P andsurrounding iris I, camera 14 determines a diameter of pupil P andidentifies a center location PC1. Similarly, using the same imagecaptured by camera 14, processor 20 also determines a diameter of theouter iris boundary B and a location of the boundary center BC1,generally by using the contrast differential between the outer irisboundary and the surrounding tissues. Based on the difference inlocation between the outer iris boundary center BC1 and the pupil centerboundary PC1, processor 20 identifies a horizontal center difference Δxand a vertical center difference Δy. For a first image at a relativelynear viewing distance as shown in Fig. A, the identified Δx1 and Δy1 areplotted as illustrated in FIGS. 3A and 3B.

Referring now to FIGS. 2, 3A and B, and 4B, a measurement taken with thevariable distance viewing target at a nearer optical viewing distanceresults in constriction of the pupil to a smaller pupil size P′.Processor 20 once again determines a size and center location of theconstricted pupil PC2 relative to the concurrent outer iris boundarycenter BC2 so as to determine new horizontal and vertical center offsetsΔx2 and Δy2. By measuring a series of different viewing distances,horizontal and vertical pupil center drift with changing viewingdistance D may be plotted as shown in FIGS. 3A and 3B.

Image processing software for use in determining the size and centrallocation of pupil P and outer iris boundary B is commercially availablefrom a number of sources. A variety of image processing softwarepackages may be used, including (for example) INTEL IMAGE processinglibraries or the like. Processors suitable for pupilometer include PCshaving the power of an INTEL Pentium® processor. Many of the processorscould also be used, including those running the MacOS operating systemfrom APPLE COMPUTERS, INC., a custom DSP device, or the like.Alternative embodiments may make use of software modified from that of acommercially available pupilometer, such as the P2000 line ofpupilometers sold by PROCYON of the United Kingdom.

So as to effectively measure pupil center drift, pupil size, pupilroundness, and other physiological changes throughout a range of viewingdistances, it will often be advantageous to include a variable distanceviewing target system 18 capable of varying an optical viewing distancebetween eye location 12 and a target from no more than about 1 meter toat least about 3, and often at least about 5 meters. Exemplary variabledistance viewing target systems 18 will provide a plurality ofintermediate viewing distances between a nearest viewing distance and afarthest viewing distance. In some embodiments, particularly wherehysteresis appears to be an issue, processor 20 may calculate differentrelationships between pupil center drift and viewing distance, with onerelationship for pupil constriction (going from a far viewing distanceto a near viewing distance) and one for pupil expansion (going from anear viewing distance to a far viewing distance). Still further pupilcenter drift measurements may be recorded and/or analyzed, includingpupil center drift at differing viewing brightnesses, such as atphotopic viewing conditions, scotopic viewing conditions, andintermediate light viewing conditions.

Referring now to FIG. 5, when a patient having eyes E1 and E2 is viewinga near-distance viewing target 32, the optical axes of the eyes define afirst vergence angle V1. As the eyes shift in viewing distance from thenear viewing target 32 to the far viewing target 34, the vergence angleof eyes E1, E2 changes to a second vergence angle V2. The pupilometersdescribed herein will preferably accommodate such changes in thevergence angle with changes in viewing distance, particularly forbinocular versions of the pupilometer.

Referring now to FIG. 6, optical components of pupilometer 10 are shownin more detail. As described above, an optical path 16 extends from aneye location 12 to camera 14. Eye location 12 is defined by an eye cup34 which engages tissue around eye E. A housing 36 isolates the opticalcomponents of the eye and the optical pans of the pupilometer fromambient light, and structurally supports the optical components of thepupilometer. Optionally, housing 36 may form one half of a binocularpupilometer, with the other portion of the pupilometer being disposed onthe other side of a center line CL for the patient's other eye.

So as to accommodate changes in vergence angle of eye E, optical path 16is reflected by a movable mirror system including a translatable mirror38 and/or an angularly displaceable mirror 40. These movable mirrors maybe driven by galvanometer or other electrically driven actuators, oftenper signals received from processor 20. Other embodiments may make useof manually repositioned mirrors which change position and/or angle inresponse to manual inputs from outside housing 36.

In the embodiment of FIG. 6, a portion of the imaging optical path 16 isseparated from a target optical path 42 by a beam splitter BS ofvariable viewing distance system 18. In other embodiments, the targetoptical path and imaging optical path may be separated alongsubstantially their entire length, particularly when imaging of the eyetakes place from off the optical axis of the eye. An off-axis eyetracker which might be modified to measure pupil center drift isdescribed in more detail in U.S. patent application Ser. No. 09/545,240,entitled “Two Camera Off-Axis Eye Tracker for Laser Eye Surgery” asfiled on Apr. 7, 2000 (Attorney Docket No. 018158-016210), now issued asU.S. Pat. No. 6,322,216, the full disclosure of which is incorporatedherein by reference.

In the schematic illustration of FIG. 6, along with a viewing targetimage 44, variable distance viewing system 18 includes a zoom lenssystem 46 for changing an optical viewing distance between eye location12 and target 44. Zoom lens system 46 will include motors or the likefor repositioning lenses so as to change the optical path distance inresponse to signals form the processor. Alternative embodiments may havea manual system for actuating the zoom lenses with a zoom positionsensor providing signals to the processor, or may rely on manual inputof the zoom position.

Alternative variable distance viewing targets are also possible,including systems which rely on removal and replacement of one or moreoptical components. For example, one or more of the lens of the variabledistance viewing system may be mounted on a turret so that a first lenscan be rotated out of the target optical path 42 and replaced by anotherlens of the turret. In some embodiments, target image 44 may simply bemoved a greater distance away from other optical components, or may bereplaced by another target at a farther viewing distance.

Still further alternative pupilometer structures may be employed,including that schematically illustrated in FIG. 7. The opticalcomponents of pupilometer 110 are described in more detail in U.S.patent application Ser. No. 10/872,331, filed on Jun. 17, 2004, andentitled “Correction of Presbyopia Using Adaptive Optics and AssociatedMethods” (Attorney Docket No. 018158-025400US), the full disclosure ofwhich is incorporated herein by reference. Along with allowing imagingand measurement of the pupils or other physiological changes the eyes inresponse to changes in viewing distance, pupilometer 110 includesdeformable mirrors and Hartmann-Shack wavefront sensors for modelingrefractive changes to the eyes and measuring optical aberrations of theeyes. More specifically, pupilometer 110 generally includes an opticalpath 112R coupling an adjustable target 114 with a right eye 116R of apatient. A similar optical path 112L couples adjustable target 114 witha left eye 116L, thereby providing a binocular viewing system.Adjustable mirrors or the like such as those described above regardingFIG. 6 may be included so as to accommodate changes in vergence anglebetween the eyes. As the components of the optical path, sensors, andthe like of pupilometer 110 along the right optical path 112R aregenerally similar to those of the left optical path 112L, only the rightside need be described to understand the structure and use of theapparatus.

Optical path 112 includes a series of lenses L and mirrors M opticallycoupling adjustable target 114 to right eye 116R via a deformable mirror118R. A Hartmann-Shack wavefront sensor HS is coupled to optical path112R by a beam splitter BS for measurement of aberrations of eye 116R. Asensor 120 is also coupled to the optical path 112R by one or more beamsplitters BS for measurement of a size of a pupil of eye 116R,measurement of pupil center drift, and the like.

Adjustable target 114 transmits an image along optical path 112R, withthe light being profiled by an aperture A having a field stop. The lightis collimated by an adjustable focal length lens L before being directedalong the optical path using a prism P. At the end of the optical pathadjacent eye 116R, the light is re-collimated by lenses L to go throughthe optics of the eye, primarily the cornea and the lens of the eye, soas to form an image on the retina.

When pupilometer 110 is used for measuring pupil center drift,deformable mirror 118R may be in a flat configuration or may beconfigured so as to compensate for refractive errors of the eye 1116R.Regardless, the patient will view the viewing target 114 at the desiredviewing distance. Sensor 120, which will often comprise a CCD or thelike as described above regarding camera 14, will obtain an image of eye116R. Sensor 120 will transmit appropriate image signals to computercontrol system 122 so as to allow the pupil center location relative tothe outer pupil boundary (or the like) to be determined, along withpupil size or any other desired physiological characteristics.Adjustable viewing target 114 may then be revised to a new viewingtarget distance, and the process repeated.

As described in more detail in U.S. patent application Ser. No.10/872,331, computer control system 122 may drive deformable mirror 118Rin response to signals from another CCD 126 associated with theHartmann-Shack sensor HS. This may allow the deformable mirror tocompensate for and measure the ocular aberration of the eyes. Ambientlighting 124 may also be under the control of computer system 122 so asto measure pupil properties at different lighting conditions.

While the exemplary embodiments have been described in some detail forclarity of understanding and by way of example, a variety ofadaptations, modifications, and changes will be obvious to those ofskill in the art. For example, the processor may employ dynamicthresholding in measurements of the pupil and outer iris boundary.Rather than estimating the shape of the outer iris boundary from only aportion of that structure, the method may employ a speculum in the eyeduring pupil center drift measurements so that the entire outer irisboundary is within the field of view of the image capture device. Asingle camera may be used to measure pupils of both eyes in binocularsystems, with the optical paths from the eyes optionally being separatedadjacent the image sensing surface of the camera by a shield or thelike, as described in U.S. Pat. No. 5,784,145, the full disclosure ofwhich is incorporated herein by reference. Hence, the scope of thepresent invention is limited solely by the appended claims.

1. A pupilometer comprising: an optical sensor including an imagecapture device having an image detection surface; a sensing optical pathcoupling the sensor with an eye measurement location, wherein thesensing optical path images at least a sufficient portion of the pupiland the outer iris boundary of an eye disposed at the eye measurementlocation onto the image detection surface of the image capture device sothat the pupilometer can determine a center of the pupil relative to acenter of the outer iris boundary; a variable distance viewing targetsystem; and, a processor coupled to the optical sensor and the variabledistance viewing target system, the processor having tangible mediaembodying machine-readable code for determining a relationship between:changes in viewing distance between the eye measurement location and thevariable distance viewing target system, and pupil center drift of thepupil relative to the outer iris boundary of the eye disposed at the eyemeasurement location.
 2. The pupilometer of claim 1, wherein thevariable distance viewing target system has an associated near viewingconfiguration and an associated far viewing configuration.
 3. Thepupilometer of claim 2, wherein the variable distance viewing targetsystem in the near viewing configuration is optically separated from theeye measurement location by no more than 1 m.
 4. The pupilometer ofclaim 3, wherein the variable distance viewing target system with thefar viewing configuration is optically separated from the eyemeasurement location by 5 m or more.
 5. The pupilometer of claim 2,wherein the variable distance viewing target system is coupled to theeye measurement location by at least a portion of the sensing opticalpath.
 6. The pupilometer of claim 2, further comprising a target opticalpath coupling the variable distance viewing target system to the eyemeasurement location, at least a portion of the target optical pathbeing offset from the sensing optical path, and an optical length of thetarget optical path varying with changes in configuration of thevariable distance viewing target system.
 7. The pupilometer of claim 6,wherein changes in configuration of the variable distance viewing targetsystem are effected using at least one member selected from the groupconsisting of: a movable target image; a plurality of alternativelyselectable target images having differing target optical path lengths;an optical zoom; and a turret of alternative selectable optical elementsalong the target optical path.
 8. The pupilometer of claim 2, whereinthe variable distance viewing target system has at least one associatedintermediate viewing configuration with a sensing optical path lengthgreater than that of the near-viewing configuration and shorter thanthat of the far-viewing configuration.
 9. The pupilometer of claim 1,wherein the pupilometer comprises a binocular pupilometer with anothersensing optical path coupled to another eye measurement location, theprocessor configured to determine another relationship between changesin viewing distance and pupil center drift relative to the outer irisboundary of another eye of the patient at the other eye measurementlocation while the first eye is at the eye measurement location.
 10. Thepupilometer of claim 9, further comprising another optical sensor in theother sensing optical path, the other sensor coupled to the processor.11. The pupilometer of claim 9, wherein the optical sensor is coupled tothe other eye measurement location by the other sensing optical path.12. The pupilometer of claim 9, wherein a first optical axis extendsfrom adjacent the eye measurement location toward the variable distanceviewing target system, and wherein a second optical axis extends fromadjacent the other eye measurement location toward the variable distanceviewing target system, and wherein a vergence angle between the firstand second optical axes changes when the variable distance viewingtarget system changes between a near-viewing configuration and afar-viewing configuration.
 13. The pupilometer of claim 1, wherein theimage capture device comprises a CCD sensitive to IR light.
 14. Thepupilometer of claim 1, wherein the processor records a plurality ofrelative pupil centers and associated pupil sizes and viewing distances.15. A binocular pupilometer comprising: an image capture system; a firstsensing optical path coupling the image capture system with a first eyemeasurement location, the first optical sensing path having a firstoptical axis extending from adjacent the first eye measurement location;a second sensing optical path coupling the image-capture system with asecond eye measurement location, the second optical sensing path havinga second optical axis extending from adjacent the second eye measurementlocation; a variable distance viewing target system having: a targetimage; a first configuration; a second configuration; a first viewingdistance between the target image and the first and second eyemeasurement locations when in the first configuration; a second viewingdistance between the target image and the first and second eyemeasurement locations when in the second configuration, the seconddistance being different from the first distance; and, a vergence anglebetween the first optical axis and the second optical axis varying whenthe variable distance viewing target system changes between the firstconfiguration and the second configuration; and a processor coupled tothe image-capture system and the variable distance viewing targetsystem, the processor having tangible media embodying machine-readablecode for determining the relationship between changes in viewingdistance between the eye measurement location and the variable distanceviewing target system, and pupil center drift of the pupil relative tothe outer iris boundary of the eye disposed at the eye measurementlocation and the processor configured to determine a relationshipbetween: a change in the viewing distances from the first configurationto the second configuration; and, the pupil center drift of the pupilrelative to the outer iris boundary of the eye disposed at each eyemeasurement location.
 16. A pupil measurement method comprising:capturing a first image of a first eye while the first eye is viewing ata first viewing distance; capturing a second image of the first eyewhile the first eye is viewing at a second viewing distance, the secondviewing distance being different from the first viewing distance; anddetermining the pupil center drift relative to the center of the outeriris boundary of the first eye from the first and second captured imagesof the first eye.
 17. The pupil measurement method of claim 16, furthercomprising: capturing a first and a second image of a second eye whilethe second eye is viewing at a first and a second viewing distance,respectively, wherein the first and second eyes are viewing at the firstviewing distance simultaneously, and wherein the first and second eyesare viewing at the second viewing distance simultaneously; anddetermining the pupil center drift relative to the iris boundary of thesecond eye from the first and second captured images of the second eye.18. The pupil measurement method of claim 17, wherein a vergence anglebetween a first optical axis of the first eye and a second optical axisof the second eye varies when the variable distance viewing targetsystem changes between the first viewing distance and the second viewingdistance.
 19. The pupil measurement method of claim 16, furthercomprising: determining a first size of the first pupil from the firstimage of the first eye, a second size of the first pupil from the secondimage of the first eye, and a relationship between pupil size andviewing distance.